1. Field
The present invention relates to devices, systems, and processes useful as an assistance feature to supplement an operator's control input to a vehicle.
2. Description of the Related Art
Vehicles have typically included a system(s) that assist the operator's input for the control of the vehicle. This assistance can supplement the operator's control of the vehicle to enhance comfort for the operator/passenger(s) and/or to enhance dynamic performance of the vehicle. Examples of an operator assistance system can include, but are not limited to, power steering systems, anti-lock braking systems (ABS), traction control systems (TCS), stability assistance systems (aka, VSA, VSC or ESP)—which can be, active suspension systems, all-wheel drive systems (AWD) and four-wheel steering systems (4ws). Some of these operator assistance systems can signal the operator to alter their input through visual, aural or tactile notification. Examples of these systems can include, but are not limited to, active braking systems, lane departure warning systems, parking assistance systems and obstacle avoidance systems. Each of these operator assistance systems are generally known in the art.
The operator assistance system can include a controller—also called an electronic control unit (ECU) or a central processing unit (CPU)—at least one sensor, and at least one actuator in electrical communication with the ECU. The ECU often relies on data generated by a steering angle sensor so that the ECU can interpret the operator's input and send an appropriate signal(s) to the appropriate actuator(s) to supplement the operator's input.
In many of these operator assistance systems, it can be advantageous for the ECU to rely on data from the steering angle sensor to determine whether the vehicle operator is attempting to steer the vehicle to the left or to the right relative to a neutral position, as well the magnitude of the directional change (relative to the neutral position) intended by the operator. Typically, the neutral position corresponds to the position of the steering system components and the steering angle sensor when the vehicle travels along a substantially straight path. It is known in the art to position the steering angle sensor within the steering system of the vehicle such that the steering angle sensor can detect the operator's steering input. The steering angle sensor can be an absolute position or a relative position sensor. Both types of steering sensors and their implementation are known in the art.
An absolute position sensor can indicate, at any time, the position of the steering wheel relative to the neutral position. As a result, an absolute steering position sensor can be a complicated device and can be expensive to produce. Further, in some of these operator assistance systems, it may be unnecessary to determine the neutral position for appropriate operation of the system. Thus, an absolute position sensor can increase the cost and/or complexity of the operator assistance system with no corresponding benefit.
In contrast, a relative position sensor can be less complex in design and less costly compared to an absolute position sensor. However, a relative position sensor can detect only a change in position of the steering wheel relative to the previously detected position. Thus, the raw sensor data can neither indicate the direction relative to the neutral position to which the operator has turned the steering wheel nor indicate how far from the neutral position the operator has turned the steering wheel. In order to translate the raw sensor data into absolute position data, additional electronic circuitry and/or software can be provided in the sensor assembly, or in the ECU, so that the neutral position can be determined either by the sensor or the ECU. This additional circuitry can offset or exceed the cost and/or the complexity advantage(s) that the relative position sensor can have over an absolute position sensor.
Operator assistance systems known in the art that employ a relative position sensor and also rely on determination of the neutral position typically do not store the neutral position of the steering angle sensor after the vehicle is shut down. Thus, the neutral position determination algorithm is performed each time the vehicle is started. Operation of this algorithm is dependent on a particular travel path(s) taken by the vehicle. As such, it can take a finite period of time to complete. Thus, the vehicle assistance system can be rendered ineffective prior to completion of the neutral position determination algorithm.
There is, and has been, a need to provide a system and method that can obtain and process real-time data indicative of the operator's steering direction input (i.e., left or right) and the magnitude of the steering input (i.e., how far from neutral the driver has rotated the steering wheel) via a relative position sensor as close to vehicle start-up as possible, where the system and method are relatively simple in design and have a minimum cost.
In order to provide the operator assistance system utilizing a relative position steering angle sensor with relevant steering angle data, there is a need to provide an estimated steering angle that can approximate the actual angle of the steerable wheels of the vehicle until the neutral position algorithm is complete.
Further, a failure of the steering sensor or interruption of data from the sensor can cause the operator input assistance system to shut down (or otherwise be impaired to a certain degree) until the failure or interruption is resolved, thereby canceling the assistance to the operator's input. Thus, there is a need to provide a failure mode where the steering angle can be approximated from at least one other vehicle dynamic sensor so that the operator input assistance system can operate in a sufficient manner despite a failure of the steering angle sensor.